Transforming growth factor-beta (TGF-beta) exerts an inhibitory effect on epithelial cell proliferation while insulin-like growth factor-1 (IGF-1) is a positive regulator of proliferation and together they may participate in driving neoplastic progression. The regulation of TGF-beta1 and IGF-1 gene expression was analyzed in an in vitro model of an estrogen receptor positive (ER+), non-metastatic (MCF-7) and an (ER-), metastatic (MDA-MB-435) breast cancer cell line, respectively. Our results indicate a loss of the regulation of TGF-beta1 and the gain of the expression and upregulation of IGF-1 pathways during malignant progression. These data demonstrate that two factors, convergent on cell growth, can have divergent roles in the regulation of the expression of TGF-beta1.